Currently-implemented wireless communication networks provide for reference signals (e.g., pilot signals) to be transmitted from a base station to subscriber stations in its coverage area. The subscriber stations use the reference signals to estimate channel conditions. However, transmitting each reference signal uses a significant amount of overhead. The time-frequency slots allocated to the transmission of each reference signal could be used by the base station to transmit data if the reference signal did not need to be transmitted.
Conventional base stations, which have an antenna array with multiple physical antennas, transmit a different reference signal over each physical antenna in the antenna array regardless of the number of channels currently being used. For example, if the antenna array has four antennas but only two data streams are being transmitted, the base station still transmits four reference signals—one over each antenna. This results in wasted time-frequency resources for the additional reference signals. One solution to this problem is to transmit fewer reference signals when transmitting fewer than all data streams and to turn off antennas not being used. However, this results in bursty interference for neighboring cells as the antennas are turned off and on. Therefore, there is a need in the art for an improved method for generating reference signals in a wireless communication system.